Patty Duke, who as a teen won an Oscar for playing Helen Keller in "The Miracle Worker" and maintained a long and successful career throughout her life while battling personal demons, has died at the age of 69.

Duke's agent, Mitchell Stubbs, says the actress died early Tuesday morning of sepsis from a ruptured intestine. She died in Coeur D'Alene, Idaho, according to Teri Weigel, the publicist for her son, actor Sean Astin.

Duke found early success playing the young Keller first on Broadway, then in the acclaimed 1962 film version, both with Anne Bancroft as Helen's teacher, Annie Sullivan.

Then in 1963, she burst on the TV scene starring in a sitcom, "The Patty Duke Show," which aired for three seasons. She played dual roles under an unconventional premise: as identical cousins living in Brooklyn, New York.

In 2015, she would play twin roles again: as a pair of grandmas on an episode of "Liv and Maddie," a series on the Disney Channel.

"We're so grateful to her for living a life that generates that amount of compassion and feeling in others," Astin told The Associated Press in reflecting on the outpouring of sentiment from fans at the news of her death.

She had "really, really suffered" with her illness, Astin added. From late last week until early Tuesday morning, he said, "was a really, really, really hard process. It was hard for her, it was hard for the people who love her to help her...."

Born Anna Marie Pearce in Queens, New York, on Dec. 14, 1946, Duke had a difficult childhood with abusive parents. By 8 years old she was largely under the control of husband-and-wife talent managers who soon found her work on soap operas and print advertising.

In the meantime, they supplied her with alcohol and prescription drugs, which accelerated the effects of her undiagnosed bipolar disorder.

In her 1988 memoir, "Call Me Anna," Duke wrote of her condition and its diagnosis only six years earlier, and of the treatment that subsequently stabilized her life. The book became a 1990 TV film in which she starred, and she became an activist for mental health causes, helping to de-stigmatize bipolar disorder.

With the end of "The Patty Duke Show" in 1966, which left her stereotyped as not one, but two squeaky-clean teenagers, Duke attempted to leap into adulthood in the 1967 melodrama "Valley of the Dolls," in which she played a showbiz hopeful who falls prey to drug addiction, a broken marriage and shattered dreams.

The film, based on the best-selling Jacqueline Susann pulp novel, was critically slammed but a commercial smash.

During her career she would win three Emmy Awards, for the TV film "My Sweet Charlie," the miniseries "Captains and the Kings" and the 1979 TV remake of "The Miracle Worker," in which Duke played Annie Sullivan and "Little House on the Prairie" actress Melissa Gilbert as Keller.

In the 1980s, she starred in a trio of short-lived sitcoms: "It Takes Two," ''Karen's Song" and "Hail to the Chief," in which she was cast as the first female president of the United States.

She starred in several stage productions, including a return to Broadway in 2003 to play Aunt Eller in a revival of the musical "Oklahoma!"

By then, she already had spent a dozen years living in Idaho with her fourth husband, Michael Pearce (who survives her), seeking refuge from the clutter, noise and turmoil of big cities, and from the tumultuous life she had weathered in the past.

In describing the role of Aunt Eller, and perhaps herself, to The Associated Press, she said, "This is a woman who has had strife in life, made her peace with some of it and has come to the point of acceptance. Not giving up."